Thanks for the suggestion. I installed the attached. Although it doesn't
go quite as far as your suggestion, it should adequately warn people who
pay attention to warnings.From a0c3e5648be9727d1e2e18f18f143c619f825706 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 30 Dec 2024 11:38:56 -0800
Subject: [PATCH] date: improve doc for ambiguous formats
Problem reported by Tim Connors <https://bugs.gnu.org/75208>.
* doc/coreutils.texi (Date conversion specifiers):
* src/date.c (usage):
Warn about ambiguous formats like %D.
---
doc/coreutils.texi | 11 ++++++++---
src/date.c | 10 +++++-----
2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 11a51706b..5a68ab517 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -16656,7 +16656,9 @@ It is normally at least two characters, but it may be more.
@item %d
day of month (e.g., @samp{01})
@item %D
-date; same as @samp{%m/%d/%y}
+date; same as @samp{%m/%d/%y}.
+Although commonly used in the US, this format is confusing elsewhere,
+and it is ambiguous for dates in different centuries.
@item %e
day of month, space padded; same as @samp{%_d}
@item %F
@@ -16672,6 +16674,7 @@ year corresponding to the ISO week number, but without the century
as @samp{%y}, except that if the ISO week number (see
@samp{%V}) belongs
to the previous or next year, that year is used instead.
+This format is ambiguous for dates in different centuries.
@item %G
year corresponding to the ISO week number. This has the
same format and value as @samp{%Y}, except that if the ISO
@@ -16710,9 +16713,11 @@ week number of year, with Monday as first day of week
(@samp{00}@dots{}@samp{53}).
Days in a new year preceding the first Monday are in week zero.
@item %x
-locale's date representation (e.g., @samp{12/31/99})
+locale's date representation (e.g., @samp{12/31/99}).
+This format can be ambiguous for dates in different centuries.
@item %y
-last two digits of year (@samp{00}@dots{}@samp{99})
+last two digits of year (@samp{00}@dots{}@samp{99}).
+This format is ambiguous for dates in different centuries.
@item %Y
year. This is normally at least four characters, but it may be more.
Year @samp{0000} precedes year @samp{0001}, and year @samp{-001}
diff --git a/src/date.c b/src/date.c
index ee32403ef..2245136bc 100644
--- a/src/date.c
+++ b/src/date.c
@@ -200,13 +200,13 @@ FORMAT controls the output. Interpreted sequences are:\n\
fputs (_("\
%C century; like %Y, except omit last two digits (e.g., 20)\n\
%d day of month (e.g., 01)\n\
- %D date; same as %m/%d/%y\n\
+ %D date (ambiguous); same as %m/%d/%y\n\
%e day of month, space padded; same as %_d\n\
"), stdout);
fputs (_("\
%F full date; like %+4Y-%m-%d\n\
- %g last two digits of year of ISO week number (see %G)\n\
- %G year of ISO week number (see %V); normally useful only with %V\n\
+ %g last two digits of year of ISO week number (ambiguous; 00-99); see %G\n\
+ %G year of ISO week number; normally useful only with %V\n\
"), stdout);
fputs (_("\
%h same as %b\n\
@@ -243,9 +243,9 @@ FORMAT controls the output. Interpreted sequences are:\n\
%W week number of year, with Monday as first day of week (00..53)\n\
"), stdout);
fputs (_("\
- %x locale's date representation (e.g., 12/31/99)\n\
+ %x locale's date (can be ambiguous; e.g., 12/31/99)\n\
%X locale's time representation (e.g., 23:13:48)\n\
- %y last two digits of year (00..99)\n\
+ %y last two digits of year (ambiguous; 00..99)\n\
%Y year\n\
"), stdout);
fputs (_("\
--
2.45.2
